Miniature spectrometer

ABSTRACT

A miniaturized spectrometer is adapted for placement within a body near tissue to be characterized. The spectrometer includes a light source and a plurality of light detectors. The light source generates light to illuminate the tissue. The detectors detect optical signals from the illuminated tissue and convert these optical signals to electrical signals. The miniaturized spectrometer can be disposed at the distal end of an interventional device. Optical conduits, such as fiber optic cables or strands, extending the length of the interventional device are not required when the miniature spectrometer is employed.

CROSS-REFERENCE TO RELATED APPLICATION

This is based on U.S. provisional patent application Ser. No.60/033,334, filed Nov. 21, 1996.

TECHNICAL FIELD

This invention relates to a spectrometer and, more particularly, to aminiature spectrometer for placement within a body for tissuecharacterization.

BACKGROUND INFORMATION

Spectral analysis of living tissue can be used to detect various formsof cancer and other types of diseases. In spectral analysis, lightilluminates tissue region under examination and a light detector detectsoptical properties of the illuminated tissue region by measuring lightenergy modified by its interaction with the tissue region in apre-determined frequency and amplitude domain. Optical propertiesinclude absorption, luminescence, fluorescence, frequency andtime-domain responses to various materials injected to the tissue regionand other electromagnetic responses. Diseased tissue may be identifiedby comparing a spectrum obtained to spectra of normal tissue obtainedunder the same controlled conditions.

Current devices available for tissue characterization using spectralanalysis include night vision sensing systems with filtering adapted tobe used with endoscopes and multichannel fiber optic delivery systems.The latter systems typically include a light source, an optical conduit,a light applicator and receiver, a second light conduit, a spectrometerand a display unit. These systems tend to be very expensive, to requirelarge accompanying electronic systems, and to be complex requiringoperator training.

The optical fibers used as optical conduits in the multichannel fiberoptic delivery systems are source of design difficulties. In order totransport an adequate amount of light energy from the light source to atissue region inside a body, a significant amount of optical fibers mustbe included in an interventional device. An interventional device, suchas a catheter, however, does not include a lot of space and higherquality optical fibers, which take up less space, are expensive.

Optical fibers also lack mechanical properties necessary to be used withan interventional device. Optical fibers can break when flexed and havea relatively high stiffness compared to conventional catheter materials.Therefore, it is difficult to design a flexible tip for a catheter,which includes optical fibers and overall flexibility of aninterventional device which include optical fibers is limited.

Furthermore, optical fibers require an expensive terminating connectorand must be properly coupled to afford adequate light throughput. Signalefficiency of fiber based devices depends greatly upon the devices'ability to couple sufficient light into the fibers at the desiredwavelength. For spectral analysis, filtered broadband light sources arepreferred over laser light sources for cost and frequency versatility.However, it is a challenge to efficiently couple light from a lampsource into fibers with small diameters. Although laser light is moreeasily coupled into optical fibers, laser light sources are generallymore expensive, are obtainable in only a few selected wavelengths, andare subject to more critical regulatory controls than other lightsources. Furthermore, light emitted by the subject illuminated by alaser light tends to be weak and is also subject to all of the lossmechanisms and inefficiencies problematical to a laser system.

Additional hardware, such as connectors and couplers, and the need toprovide one or more optical conduits along the length of theinterventional device, make conventional devices used for spectralanalysis relatively expensive, inconvenient, and perhaps impractical.

SUMMARY OF THE INVENTION

In one aspect, the invention features a miniature spectrometer for usein spectral analysis. The spectrometer includes a light source and alight detector for placement inside a body such that optical conduitsare not necessary to deliver light signals to and from tissue inside thebody. The miniature spectrometer includes the light source and one ormore light detectors. The light source illuminates a tissue region andthe light detectors detect optical properties of the illuminated tissueby measuring modified light signals. The light detectors convert opticalsignals to electrical signals such that one or more electrical wiresplaced inside an interventional device can deliver the electricalsignals from the tissue to a signal display or a microprocessor.

Embodiments of this aspect of the invention include the followingfeatures. The light source and the light detectors are energized by anexternal power supply through electrical wires. In another embodiment,an optically transparent tip encapsulates a spectrometer. The tip isshaped to optimize tissue contact and optical transmission. The tipencapsulating the spectrometer is disposed at a distal end of aninterventional device. The tip may be coated with a material to improvelight transmission. The tip may include at least one fluid channel,which is in communication with a lumen inside the interventional device,to deliver a fluid to a tissue region. In one disclosed embodiment, aspectrometer of the invention includes a light source and the lightdetectors formed on a single substrate. The light source may be a lightemitting diode and the light detectors may be a photodiode comprisingmultiple channels, where both devices are formed on a silicon substrate.The light detector can include multiple channels to detect lightemission at multiple wavelengths.

In another aspect, the invention features a method for characterizingtissue. According to the method, a spectrometer which includes a lightsource and a plurality of light detectors is provided. The spectrometeris placed inside a body near a tissue region to be characterized. Thelight source and the detectors are connected to a power source throughelectrical wires. The energized light source generates light andilluminates the tissue region. The detectors measure light signalsmodified as a result of interacting with the tissue region. The lightdetectors convert received optical signals to electrical signals. In oneembodiment of this aspect of the invention, an optically transparent tipencapsulates the spectrometer and is located near a distal end of aninterventional probe. The method can further include the step ofrotating the spectrometer with respect to the tip. The rotation adjustsoptical properties of the light transmitted to illuminate the tissue.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

FIG. 1A is a block diagram of a system for spectral analysis including aspectrometer module in communication with external components.

FIG. 1B shows a light detector of the spectrometer module of FIG. 1A incommunication with an alternative electronic system for signal analysis.

FIG. 2A is a view in cross-section of a spectrometer module disposed ata distal end of an interventional device, the cross-section being alongline 2A-2A of FIG. 2B.

FIG. 2B is a view in cross-section of the distal end of the spectrometermodule of FIG. 2A.

FIG. 3 is a schematic diagram of an interventional device and aspectrometer module disposed at the distal end of the interventionaldevice.

FIG. 4 is a view in cross-section of the spectrometer module of FIG. 2Aencapsulated by a tip and disposed at the distal end of aninterventional device.

FIG. 5 is a view in cross-section of a single substrate spectrometermodule, the cross-section being along the length of the module.

DESCRIPTION

Referring to FIG. 1A, the spectrometer module 1 includes a light source3 and a multichannel light detector 5 in close proximity to each otherand to a region of interest 6. The region of interest 6 may be livingtissue located inside a body. The light source 3 and the light detector5 are located in close proximity to the region of interest so that theymay both emit and/or couple the light energy efficiently with minimumintervening space or material. The light source 3 is in communicationwith a power supply or source 7 through a DC power line 9, and the lightdetector 5 is in communication with the power source 7 through a biassupply line 10. The power source 7 may provide direct current (DC) ofeither high or low voltage, alternating current (AC) of an appropriatefrequency, or a pulse. AC power may be supplied to the light source 3for the purpose of modulating the light source with a modulator 17.Alternatively, current with complex waveforms may be supplied to thelight source 3. A diode may be placed in the circuit at the light source3 to rectify some of the AC power so that it can be used to bias thedetector 5. In the disclosed embodiment, a metering device 19 is placedat the source of power and employs a current sampler 20 in line tomonitor and display the power applied to the light source 3. Thisconfiguration may be used to help calibrate the instrument during use.

One or more output lines 13 extend from the detector 5 to amicroprocessor 25 and a display 11 through an amplifier 21 and an A-Dconverter 23. The output lines 13 may be shielded to reduce noisepickup. The output of the detector 5 is amplified through an amplifier21 and sent to an analog-to-digital (A-D, A/D, or A-to-D) converter 23.The digitized signal can then be sent to a microprocessor 25 or otherlogical device for subsequent spectral analysis. An alternative signalprocessing system is shown in FIG. 1B.

Referring now to FIG. 1B, the alternative signal processing systemincludes a centering scale meter 33 driven by a DC source 34 placed inthe common return line 38 extending from the light detector 5. Thisalternative signal processing system may be used to observe thedifferent signal amplitudes of optical signals received by two or morechannels of the light detector 5 operating simultaneously, or thenormalized output of the light source versus the light energy receivedby the light detector 5. The amplitude of the reading may be used todetermine the slope of the response signal relative to the input signalor to perform other more complex functions. It should be understood atthis point that an equivalent operation may be obtained using a singlechannel light detector as long as a response property of the channel isvaried over time. It may be possible to vary the response property byusing, for example, one or more filters. In the case of a single channellight detector, the two signals may be obtained sequentially, ifdesired. The functions provided by the above-described circuitry may beachieved with other or additional electrical, mechanical, and/or opticalapparatus without departing from the spirit and scope of the invention.

Referring to FIGS. 2A and 2B, a spectrometer module 41 is disposed at adistal tip of an interventional device 4. The spectrometer module 41 isplaced inside a housing 43. The housing 43 comprises an opticallytransparent material. The diameter of the housing 41 is small enough toallow the spectrometer module 41 and the housing 43 to pass throughvarious lumens of catheters and body lumens such as vascular andnonvascular vessels. For example, the housing 43 for a spectrometermodule 41 used with a catheter 4 has a maximum diameter of about 0.25inches. The housing 43 for a spectrometer module 41 used with aguidewire-sized device may have a maximum diameter of about 0.081inches.

The spectrometer module 41 includes a light source 3, two lightdetectors 61, a lens 47, a light amplifier 49, and a window 55. Thelight source 3 is a semiconductor diode source, mounted such that theoutput end 45 is facing the distal end of the module 41, which isgenerally in line with the central axis of the interventional device 4.Alternatively, the light source 3 may be positioned such that the outputend faces a direction transverse to the center axis of theinterventional device 4. Light generated by the light source 3 maydirectly illuminate a tissue region or may be focused by a lens 47before illuminating the tissue region. The lens 47 may be shaped tofocus the light into a desired pattern, or may be used to diffuse thelight if needed. A frequency multiplier 49 is placed in the path oflight generated by the light source 3 to amplify the frequency of thelight output. The frequency multiplier 49 comprises an opticallynonlinear substance. The optically nonlinear substance 49 is held inposition with a ring holder 51, to maintain its position with respect tothe position of the light source 3. Alternatively, the nonlinearsubstance 49 may be bonded directly to the output end 45 of the lightsource 3 using an optically clear bonding material. The optically clearbonding material may be epoxy, cyanoacrylate, or sodium silicate. Thebonding material may be placed directly upon the output end 45 of thelight source 3 and its surrounding area, and the nonlinear substance 49may be placed upon the bonding material. An example of an opticallynonlinear substance suitable for use with a spectrometer module of theinvention is a potassium dihydrogen phosphate (KH₂ PO₄) or KDP crystal.In order to improve light transmission, at least one surface of the KDPcrystal may be coated with a fluoride layer that acts as a one-quarterwave matching layer 53. A window 55 is placed at the distal end of thespectrometer module 41 to protect the module. The window 55 may be heldin place by bonding the window 55 to the distal tip of theinterventional device with an adhesive 57. In a preferred embodiment,the window 55 includes a bandstop filter characteristic that attenuatesoutput frequencies of the light generated by the light source 3 whilepermitting passage of light output having a predetermined frequency.Light output permitted to pass through the filter is often in theultraviolet range, and particularly has wavelengths from about 300 nm toabout 400 nm. Such filters are generally available and known. Examplesof these types of filters include tinted glass, sandwiched dyes, andinterference filters otherwise known as dichroic filters. Alternatively,variable filtration may be employed by rotating the inner portion of themodule 41 relative to portions of another colored material, such as atinted plastic catheter sheath or a tip 81 shown in FIG. 4. The cathetersheath or the tip 81 may have differing filter characteristics owing tochanges in thickness, or due to localized dyes.

One or more light detectors 61 and filters 63 may be disposed around thenonlinear substance 49 (FIG. 2B). The light detectors 61 may be, forexample, silicon photodiodes, cadmium sulfide slabs with electrodes,charge-coupled devices, or generally any light sensors that may beminiaturized and placed within the confines of a device smaller thanabout 0.250 inches or less in diameter. The light detectors 61 may bepositioned at an angle (FIG. 2A) to aid in the collection of lightemitted by the region of interest 6. Alternatively, the light detectors61 may be disposed on a flat substrate adjacent to the lightsource 3.The light signals illuminating the region of interest are modified as aresult of interacting with the region of interest 6. The light detectors61 detect the modified light signals. The light detectors 61 may alsomonitor light emission from the light source. The light detectors 61 areenergized with the energy from the power supply 7 through a power line10 (FIG. I A). Frequency selective detectors 61 are produced bydisposing filters 63 on the light detectors 61. The filters 63 attenuateone or more frequency bands of energy received by the light detectors61. Filters 63, for example, may be of the bandpass type admittingwavelengths selectively. A specific bandpass of one filter may becentered around 380 nm, while another filter may be centered around 440nm. Signal wires 13 delivering signal output may be in the form oftwisted pairs of wires or may share a common ground path. The signalwires 13 are threaded through one or more lumens 65 of theinterventional device 4, and extend back to a suitable connector locatedon or near the proximal end of the interventional device 4.

Referring to FIG. 3, the spectrometer module 41 of FIG. 2A is disposedat the distal end of an interventional device 70. In the disclosedembodiment, the module 41 is attached to the distal end of a shaft 71,and the shaft 71 houses signal wires 9, 10, and 13. The shaft 71terminates with a small connector 73 at the proximal end. The connector73 may have one or more contacts arranged to permit electrical, optical,and mechanical connection to a mating connector. The shaft 71 also has aslidable stop 75 that may be prepositioned to allow control of the depthof placement within the body. The stop may be a collar with a colletring 77 that tightens when twisted to provide a positive stop. The shaft71 may comprise a tube, such as stainless steel hypo tube, superelastic(nitinol) tube, or the like. The advantage of such shafts is that theyare relatively rigid and allow insertion into partly occluded passages.Very small shafts may be made with metal tubes. Shafts having outsidediameters of about 0.005 inches may be provided, although in mostinstances, larger shafts with diameters of about 0.08 inches or largerare adequate. Lengths of the shafts may also vary between a fewmillimeters to over 200 centimeters. The shaft 71 may be made of a moreflexible material if desired. Multi-layered counterwound wires of smalldiameter may be used as the shaft material. These shafts have relativelyhigh lateral flexibility and good torsional stiffness, and can bepositioned to specific angles by manual twisting or by a motor. Othershafts may be comprise plastics such as polyethylene, polyimide, ornylon and may have one or more lumens. Lumens carry electrical, opticalor mechanical transmission lines, or cooling fluids. In the disclosedembodiment, the shaft 71 has a screw thread 79 at the distal end tofacilitate attachment and detachment of the module 41 to the shaft 71.One possible use of the attachment thread may be to release the module41 from the end of the shaft 71, once the module 41 is positioned insidea body, by unscrewing and releasing the module 41. The tubular shaft 71may then slide over the small connector 73, which may be left outsidethe body. The module 41 may be re-connected to the shaft 71 beforewithdrawing the module 41 from the body.

Referring to FIG. 4, the spectrometer module 41 of FIG. 2A is locatedinside an optically transparent tip 81, and the tip 81 and the module 41are disposed at the distal end of an interventional device 80. The tip81 may comprise a plastic such as polystyrene, a glass such as quartz,or alternatively be molded out of a dissolvable material such assucrose. The tip 81 includes a fluid channel 82 that is in communicationwith the central lumen 84 of the catheter body 83. The fluid channel 82may be used to provide a coupling fluid such as water at or near the tipof the device, or to inject a dye (such as india ink) or a drug (such asPhotofrin), or to collect a sample of fluid or tissue. The tip 81 mayinclude secondary filters 87. Positioning the module 41 relative to thetip 81 allows variations in the optical pathway to be obtained. Forinstance, the module 41 may be rotated within the tip 81, such thatsecondary filters line up with one or more of the detectors 61 or lightemitted from the light source 3.

A catheter body 83 may house the module 41, by passing the modulethrough the central lumen 84 of the catheter 83, to guide the module 41to the region of interest in mucosal tissue 85. The embodiment shown inFIG. 4 allows the operator to monitor a change in the tissue as a resultof a drug injections, or the selective uptake of a fluorescent dye. Theshape of the tip 81 aids in the avoidance of specular reflections oflight from the surface of the mucosal lining 85 and the displacement ofintervening materials such as bacteria which often strongly fluoresce.The tip 81 can essentially provide angle independence, while avoidingthe need for actual removal of tissue material. If the tip 81 isslightly rounded, displacement of tissue is accomplished withoutactually shearing the tissue significantly. Penetration depth may becontrolled by placing the shoulder 86 of the catheter 83 against thetissue and sliding the tip 81 relative to the catheter 83. Ranges ofextension from flush or negative clearance to about 1.0 mm or greaterprotrusion of the tip 81 beyond the shoulder 86 are practical using afriction fit between the two components. The shaft 71 (FIG. 3) and themodule 41 may be bonded to the tip 81 if desired with clear epoxy. Theadvantage of such configuration is that the entire assembly may beslidably and rotatively positioned within catheter 83. The tubular formof catheter 83 is merely exemplary. Numerous catheter sheaths and otherinterventional devices that are used to conduct fluids may be usedincluding needles, guidewires, guiding catheters, trocars, introducers,endoscopes, and stents.

The tube or the housing may be filled with an optically transparentmaterial or a diffusing material. Examples of optically transparentmaterial include epoxy, water, and oil. Examples of diffusing materialinclude particulate matter suspended in a viscous fluid, like an epoxywhich may harden or an elastomeric material which may remain flexible toconform to various anatomical conditions or be shaped into variouscatheter tips.

The interventional device of FIG. 4 may be made more useful, lessexpensive, and smaller by incorporating all of the functional elementsinto a single substrate which may be embedded, attached, disposed orimplanted in interventional devices and living tissue at will. In FIG.5, a single substrate spectrum analysis package 90 employs thesefeatures in such a compact arrangement. In the disclosed embodiment, theelements are formed on a doped, layered silicon substrate.Alternatively, the substrate 91 may be an etched printed circuit on anepoxy fiberglass resin substrate. The light emitting portion is anintegral light emitting diode arrangement 93 including etchedsemiconductor N material 95 and a diamond heat sink 97 bonded to oneside of the substrate 91. The gap 99 etched below the reference surfaceof the substrate 91 allows light energy to be directed to the mirror101, which is bonded to the piezoelectric light modulator 103. Themirror 101 may be constructed by aluminizing a portion of thepiezoelectric light modulator 103 after beveling and polishing themodulator 103. Alternatively, the mirror may include a small slab ofglass material, about 0.150 mm square and 0.010 mm thick, bonded with athin layer of epoxy resin to stack actuator in a position that allowsclearance within the gap 99. The construction of the piezoelectric lightmodulator 103 may be accomplished by bonding a single layer of LeadZirconate-Titinate (PZT) directly to the substrate 91 using a conductiveepoxy and ultrasonically welding or epoxy bonding an electrode 105 witha fine copper wire 107, which is in turn bonded to an electricalterminal post 109. The terminal posts 109 can be about 0.030 mm indiameter and about 0.328 mm in length, and they can comprise brass wiresplated with gold. A large post 110 is welded ultrasonically to the baseof substrate 91 and serves as an orientation key, a mechanicalstabilizer, and is also capable of carrying somewhat higher current.

Also etched from the substrate 91 is an avalanche photodiode (APD) array121, which serves as a very sensitive light detector. In the embodimentshown in FIG. 5, the light detector 121 has a two channel version. Morechannels, however, may be added by simply repeating the structure asfollows: deposit Silicon oxide (SiO₂) layers 123 on N material layers125, which are individually connected to posts 109 through fine wires107. The depletion layer 127 is sandwiched between the N material layers125 and the substrate 91, and may also serves as part of the commonreturn circuit to post 110. A colored light filter 131 may be positionedover one or more of the light sensitive portions of the APD such thatthe spectral response of one channel is different from that of theother. In the disclosed embodiment, a colored light filter 131 ispositioned over one channel. The filter, for example, may comprise awave filter such as a dichroic filter made of a glass, a grating, or adye. The filter 131 may be temporarily positioned over a silicon oxidelayer 123 and held in place while optical potting plastic 133 is moldedover the assembly. Materials such as polystyrene, polycarbonate andmethyl-methacrylate, for example, may be used as the optical pottingplastic to cast or injection mold a desired shape of the package 90.Other materials such as urethanes may be used to form the cast as longas they are sufficiently transmissive of light energy and are reasonablyelastic to allow small excursion such as the mirror 101. An air spacearound the gap 99 may be desirable depending on the index of refractionneeded in the vicinity of the mirror 101 and the output end of the lightemitting diode 93. One way to accomplish this is to place a premoldedframe over the gap 99, which prevents the flow of potting material intothat area. The frame may be injection molded out of the material alsobeing used for the package 90 or a material that has a higher meltingtemperature. The frame may be bonded in place with a thin layer of clearepoxy film. The package 90 may be shaped to permit modification of theoptical signals, which may enter or exit the package. In the embodimentshown, the serrated lens 135 is molded or embossed into the surface ofthe package 90. The advantage of this configuration is that a polishedmold may be used to form a precision optical surface as desired. Thestate of the art injection molding techniques and relatively lowviscosity thermoplastics such as polystyrene allow creation of very finefeatures with controllable dimensions and step heights on the surface. Adimension of the surface feature may be in the range of about 0.005 mm.Even finer features of less than 0.005 mm may be embossed using pressureand a photoetched master such that binary optical steps, holograms, orgratings capable of diffracting IR, visible, and UV light may be formeddirectly on the surface of the package 90. Creation of such features onthe surface, or within the assembly, avoids the need for additional,expensive optical components and their holders. A conventional curvedlens 137 is created on the surface of the package 90 to focus the lightenergy as desired. The conventional curved lens 137 also may be moldedto the surface during the molding operation. A grating may disperselight across the one or more detectors providing frequency selectioncapability.

Spectrometer modules according to the invention are designed to placethe light source and the light detector in proximity to a tissue regionunder spectral analysis. Tissue characterization using spectral analysisis based on the understanding that light emitted from a light sourceinteracts with the tissue and modifies the light. Absorption,scattering, and other loss of energy occurs when light interacts withthe tissue. Various tissue types, however, have differing absorption andreflection properties. Therefore, tissue can be characterized usingspectral analysis. These interaction phenomena, however, also limit thedepth of light penetration that can be achieved. Therefore, energy lossdue to extraneous factors may be severe when the light source is notlocated near the tissue of interest. The invention provides means forplacing the light source and the light detector near the tissue ofinterest, such that efficient operation can be achieved. Therefore, thespectrometer module of the invention eliminates unnecessary light lossand allows the light detector to detect light modification caused by theinteraction with the tissue.

In general, any type of light detector capable of detecting modifiedlight signals due to its interaction with the subject under analysis andcapable of being made sufficiently small to fit in an interventionaldevice may be used in accordance with the invention. For example, acharge coupled device (CCD) sensor may be arranged circumferentiallyaround the energy generating source and connected via signal wires.Alternatively, silicon photodiodes, cadmium sulfide cells orscintillation detectors may be arranged such that a returning portion ofthe lightwave energy is captured and measured. In the case of CCD typesensors, a large number of such devices may be incorporated in a verysmall area, although only one such sensor may be necessary to obtain andmeasure a useful signal. Alternatively, two or more sensors may be usedin accordance with the invention. The advantage of using multiplesensors is that it eliminates the need for changing filters. Filter xfor instance, may be arranged to admit blue lightwaves, while filter ymay be arranged to admit red lightwaves, such that the relativeintensity of two wavelengths can create a slope which may indicate aparticular tissue type or state.

Any light source capable of being placed in an interventional device maybe used according to the invention. An ordinary incandescent lightsource such as a tungsten filament light source with appropriatefiltering disposed thereon, an arc lamp, a mercury vapor lamp, a xenonflash lamp, gas discharge tubes filled with various gases, metallicvapors, an acoustically driven sonoluminescent source capable ofgenerating visible and UV light, and X-rays, a Gunn diode source ofsuper high frequency energy (SHF), light-emitting diodes, and otherlight sources capable of either long or short duration output, at longor short wavelengths may be used with the invention.

Possible light source systems and light detection arrangements aredescribed in two commonly-owned U.S. provisional patent applications,namely U.S. provisional patent application Ser. No. 60/033,333 and U.S.provisional patent application Ser. No. 60/033,335. These disclosures,and any regular U.S. patent applications converted on the basis of oneor both of these provisional applications, are hereby incorporatedherein by reference. In general, a light source system and a lightdetection system are selected for use according to the invention basedon various factors including, for example, cost, complexity,miniaturization, and therapeutic properties.

The shape of the spectrometer module of the invention may be any formsuitable for optimizing the contact between the module and the region ofinterest or optical transmission of generated light to the region ofinterest. Possible shapes include, for example, concave, stepped,cylindrical, chisel tipped, conical, convex, and hemispherical. Inaddition, the outer or inner surface of the module may be coated with aspecial material to enhance the light transmitting properties or beprovided with a microlens, a binary optical step, or a wavelengthfilter.

Although the invention has been described in terms of both the lightsource system and the light detector system, it should be understood bythose skilled in the art that the light source system alone and thedetector system alone may be used in certain circumstances where theneed arises. Furthermore, it should be understood that either the lightsource or the detector may be substituted with a non-light generating orreceiving device. Examples include radiofrequency generating andreceiving systems capable of spectroscopy at longer wavelengths, andx-ray generating and receiving systems capable of x-ray spectroscopy. Ingeneral, some of the basic features of the invention include generatinga local energy source, applying the energy source to a selected area oftissue, and collecting energy which has been modified by interactionwith the selected area of tissue. The collected energy signalspreferably are analyzed to characterize the tissue, and the resultsindicated to an operator or user.

Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and the scope of the invention asclaimed. Accordingly, the invention is to be defined not by thepreceding illustrative description but instead by the spirit and scopeof the following claims.

What is claimed is:
 1. A tissue spectroscopy device comprising:aspectrometer comprising a substrate, a light source disposed on a firstsurface of the substrate, and a light detector disposed on the firstsurface of the substrate, the light detector comprising a first channeland a second channel and a filter disposed on the first channel; anoptically transparent housing surrounding the spectrometer; and aninterventional device for delivering the spectrometer to tissue.
 2. Thetissue spectroscopy device of claim 1 wherein the optically transparenthousing comprises a first lens disposed near the light source, and asecond lens disposed near the light detector.
 3. The tissue spectroscopydevice of claim 1 wherein the spectrometer further comprises a heat sinkdisposed on a second surface of the substrate opposite the firstsurface.
 4. The tissue spectroscopy device of claim 1 wherein thespectrometer further comprises a light modulator disposed on the firstsurface of the substrate, a mirror disposed on the light modulator at anangle to receive light emitted by the light source, and an etched gapbetween the light modulator and the light source.
 5. The tissuespectroscopy device of claim 1 wherein the light detector comprises anavalanche photodiode array.
 6. The tissue spectroscopy device of claim 1wherein the substrate comprises doped silicon.
 7. The tissuespectroscopy device of claim 1 wherein the substrate comprises an epoxyfiberglass resin substrate.
 8. The tissue spectroscopy device of claim 1wherein the light detector comprises a plurality of silicon dioxidelayers disposed on an n type silicon layer.
 9. The tissue spectroscopydevice of claim 1 wherein the optically transparent housing comprises amaterial selected from a group consisting of polystyrene, polycarbonate,and methyl-methacrylate.